Avis blame clients for damages

I'm devastated with the service recently received from Avis car rental in Cape Town. We booked a car online and the day we arrived at the airport the Avis attendant upgraded us to a bigger car without extra charge. As always me and my husband inspect the car and take pictures of everything before accepting the car and leaving the bay. This is the first time we are renting a car from Avis and surly the last. They charged us with damages to a wheel rim that was like that the day we received the car. Our time stamped picture prove this and after several telephone conversations with the customer service - this is still deducted from my account and Avis doesn't care. They are blaming us and we did not cause these damages. We sent them the proof without a resolution to this problem. I am not happy with how they are dealing with this situation and with me. Hope other people read this and also stop supporting Avis car rental as they are *****ing without any shame.